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What is the least number of weightings you can use to find the counterfeit coin?

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In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

posted Jul 17, 2014 by Vrije Mani Upadhyay

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1 Solution

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Break into group of 3(A)-3(B)-3(c) weight A & B . if they both are of same weignt the fake coin is in C if they are not same then take the lighter once

Weight them one by one using the same logic as above.

Regards
Vikalp

solution Jul 24, 2014 by Vikalp Kumar



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What is the minimum number weighings that can always guarantee to determine the different coin.

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